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- Curiosities of the Sky - 25/25 -

The theory which some have preferred -- that the variability of light
is due to the differences of reflective power on different parts of
the surface -- would, if accepted, be hardly less suggestive of the
origin of these little bodies by the breaking up of a larger one,
because the most natural explanation of such differences would seem to
be that they arose from variations in the roughness or smoothness of
the reflecting surface, which would be characteristic of fragmentary
bodies. In the case of a large planet alternating expanses of land and
water, or of vegetation and desert, would produce a notable variation
in the amount of reflection, but on bodies of the size of the
asteroids neither water nor vegetation could exist, and an atmosphere
would be equally impossible.

One of the strongest objections to Olbers' hypothesis is that only a
few of the first asteroids discovered travel in orbits which
measurably satisfy the requirement that they should all intersect at
the point where the explosion occurred. To this it was at first
replied that the perturbations of the asteroidal orbits, by the
attractions of the major planets, would soon displace them in such a
manner that they would cease to intersect. One of the first
investigations undertaken by the late Prof. Simon Newcomb was directed
to the solution of this question, and he arrived at the conclusion
that the planetary perturbations could not explain the actual
situation of the asteroidal orbits. But afterward it was pointed out
that the difficulty could be avoided by supposing that not one but a
series of explosions had produced the asteroids as they now are. After
the primary disruption the fragments themselves, according to this
suggestion, may have exploded, and then the resulting orbits would be
as ``tangled'' as the heart could wish. This has so far rehabilitated
the explosion theory that it has never been entirely abandoned, and
the evidence which we have just cited of the probably abnormal shapes
of Eros and other asteroids has lately given it renewed life. It is a
subject that needs a thorough rediscussion.

We must not fail to mention, however, that there is a rival hypothesis
which commends itself to many astronomers -- viz., that the asteroids
were formed out of a relatively scant ring of matter, situated between
Mars and Jupiter and resembling in composition the immensely more
massive rings from which, according to Laplace's hypothesis, the
planets were born. It is held by the supporters of this theory that
the attraction of the giant Jupiter was sufficient to prevent the
small, nebulous ring that gave birth to the asteroids from condensing
like the others into a single planet.

But if we accept the explosion theory, with its corollary that minor
explosions followed the principal one, we have still an unanswered
question before us: What caused the explosions? The idea of a world
blowing up is too Titanic to be shocking; it rather amuses the
imagination than seriously impresses it; in a word, it seems
essentially chimerical. We can by no appeal to experience form a
mental picture of such an occurrence. Even the moon did not blow up
when it was wrecked by volcanoes. The explosive nebulŠ and new stars
are far away in space, and suggest no connection with such a
catastrophe as the bursting of a planet into hundreds of pieces. We
cannot conceive of a great globe thousands of miles in diameter
resembling a pellet of gunpowder only awaiting the touch of a match to
cause its sudden disruption. Somehow the thought of human agency
obtrudes itself in connection with the word ``explosion,'' and we
smile at the idea that giant powder or nitro-glycerine could blow up a
planet. Yet it would only need enough of them to do it.

After all, we may deceive ourselves in thinking, as we are apt to do,
that explosive energies lock themselves up only in small masses of
matter. There are many causes producing explosions in nature, every
volcanic eruption manifests the activity of some of them. Think of the
giant power of confined steam; if enough steam could be suddenly
generated in the center of the earth by a downpour of all the waters
of the oceans, what might not the consequences be for our globe? In a
smaller globe, and it has never been estimated that the original
asteroid was even as large as the moon, such a catastrophe would,
perhaps, be more easily conceivable; but since we are compelled in
this case to assume that there was a series of successive explosions,
steam would hardly answer the purpose; it would be more reasonable to
suppose that the cause of the explosion was some kind of chemical
reaction, or something affecting the atoms composing the exploding
body. Here Dr Gustav Le Bon comes to our aid with a most startling
suggestion, based on his theory of the dissipation of intra-atomic
energy. It will be best to quote him at some length from his book on
The Evolution of Forces.

``It does not seem at first sight,'' says Doctor Le Bon,

very comprehensible that worlds which appear more and more stable
as they cool could become so unstable as to afterward dissociate
entirely. To explain this phenomenon, we will inquire whether
astronomical observations do not allow us to witness this
dissociation.

We know that the stability of a body in motion, such as a top or a
bicycle, ceases to be possible when its velocity of rotation
descends below a certain limit. Once this limit is reached it loses
its stability and falls to the ground. Prof. J. J. Thomson even
interprets radio-activity in this manner, and points out that when
the speed of the elements composing the atoms descends below a
certain limit they become unstable and tend to lose their
equilibria. There would result from this a commencement of
dissociation, with diminution of their potential energy and a
corresponding increase of their kinetic energy sufficient to launch
into space the products of intra-atomic disintegration.

It must not be forgotten that the atom being an enormous reservoir
of energy is by this very fact comparable with explosive bodies.
These last remain inert so long as their internal equilibria are
undisturbed. So soon as some cause or other modifies these, they
explode and smash everything around them after being themselves
broken to pieces.

Atoms, therefore, which grow old in consequence of the diminution
of a part of their intra-atomic energy gradually lose their
stability. A moment, then, arrives when this stability is so weak
that the matter disappears by a sort of explosion more or less
rapid. The bodies of the radium group offer an image of this
phenomenon -- a rather faint image, however, because the atoms of
this body have only reached a period of instability when the
dissociation is rather slow. It probably precedes another and more
rapid period of dissociation capable of producing their final
explosion. Bodies such as radium, thorium, etc., represent, no
doubt, a state of old age at which all bodies must some day arrive,
and which they already begin to manifest in our universe, since all
matter is slightly radio-active. It would suffice for the
dissociation to be fairly general and fairly rapid for an explosion
to occur in a world where it was manifested.

These theoretical considerations find a solid support in the sudden
appearances and disappearances of stars. The explosions of a world
which produce them reveal to us, perhaps, how the universes perish
when they become old.

As astronomical observations show the relative frequency of these
rapid destructions, we may ask ourselves whether the end of a
universe by a sudden explosion after a long period of old age does
not represent its most general ending.

Here, perhaps, it will be well to stop, since, entrancing as the
subject may be, we know very little about it, and Doctor Le Bon's
theory affords a limitless field for the reader's imagination.
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A printed version of this book is available from Sattre Press
(http://csky.sattre-press.com). It includes extensive annotations, a
new introduction and all the original photographs and diagrams.